Electric furnace



Patented June 28, 1927.

UNITED STATES PATENT OFFICE.

JAMES C. WOODSON, 0F EAST PITTSBURGH, PENNSYLVANIA, ASSIGNOR T0 WESTING-HOUSE ELECTRIC MANUFACTURING OOMPANY, A CORPORATION OF PENNSYL- VAN IA.

ELECTRIC FURNACE.

Application led October My invention relates to electric furnaces andparticularly vto furnaces of the resistor t e.

yIAn object of my invention is to provide supporting and spacing meansfor resistors in electric furnaces whereby an even distribution of heatmay be effected. u

Another object of my invention is to provide supporting and spacingmeans for electric furnaces which lend themselves to siniple series,parallel or series-parallel arrangements whereby an even distribution ofheat may be obtained.

Another object of my invention is to provide refractory supporting andspacing means which lend themselves to uniform distribution and to sucharrangements of the resistors that the power input may be controlled,thereby effecting uniform temperatures within the furnace chamber.

In the accompanying drawings,

Figure 1 is a view in vertical cross section of an electric furnaceembodying my invention,

Fig. 2 is a view of a modified form of my invention whereby three groupsof resistors may be supported.

Fig. 3 is a view in section of a portion of a furnace showing thesupporting and spacing means illustrated in Fig. 2.

Referring more particularly to Fig.. 1, an electric furnace structure 11comprises a plurality of Walls 12 of refractory heat-1nsulatingmaterials enclosing a furnace chamber 13. Supporting members 14 extendlaterally from the Walls of the furnace structure llinto the furnacechamber 13 and form two rows of supports 15 and 16 respectively in theupper and lower part of' the furnace chamber 13. The supporting members14 of the lower row are identical with those of the upper row 15 withthe exception that they are in reverse relation thereto.

The supporting and spacing members 14 have a rear portion 17 whichextends into the refractory walls of the furnace 11. A plurality of lugs18 and 19 extend inwardly into the furnace chamber 13 and are inte\ gralwith the rear portion 17. The extremities of the inwardly extending lu s18 and 19 are semi-circular at the top and ave 1, i925. serial No.59,761.

straight sides extending downwardly and are larger in section thanthe'intermediate portion 21 thereby forming the flange 22 at the endsthereof.

Resistors 23 fit over the rounded top of the portion 21 and aretherefore securely held in place by reason of the flange 22. One groupof the resistors 23 is looped over two of the upper extending lugs 19 inthe upper row 15 of the supporting members 14 and underneath the singlelug 18 in the lower row 2O of supports 14 as indicated 'in Fig. 1. Thesecond group of resistors 23 is looped over one of the extending lugs 18in the upper row 15 of supporting members 14 and underneath two of theextending lugs 1.9 in the lower row 16. From the symmetry of theforegoing arrangements of the resistors, it is evident that the lengthsof all the resistor groups will be equal and since the resistors aresubstantially equal in crosssection the resistance of each of the groupswill also be substantially equal.

By means of the foregoing arrangement of resistors, a uniformdistribution of heat may be obtained as can readily be seen from thesymmetry of the spacing of the resistors along the refractory walls 12of the furnace chamber 13. The resistors 19 may be of either rod orribbon shape and obviously forms of resistors other than thoseillustrated in the drawing may be used.

By the symmetrical arrangement of resistors as shown in Fig. 1, it ispossible to have the two groups of resistors of equal length andcross-section, hence equal in ohmic resistance, connected in parallelacross the supply circuit in order that the furnace may be brought up tothe desired tempera.- ture in a comparatively short time, depending uponthe size of the furnace chamber 13, the thickness of the walls 12 andthe amount of power disposed of by the resistors. After the furnace hasattained the required temperature, the resistor groups may be eitherconnected in series, or one of them may be disconnected from the supplycircuit whereby only the required amount of power is supplied to takecare of the radiation losses of the furnace. Obviously, from thesymmetry of the location of the resistors, the heat distribution withthe `furnace chamber 13 will be substantially identical whether theseveral groups of resistors are electrically connected either inparallelseries, or series-parallel with the source of power supply.

In Fig. 2, I have illustrated another form of the supports 14illustrated in the furnace structure 11. There are four parallel rows oflaterally extending lugs attached to a rear portion 17 as illustrated bythe rows 24, 25, 26 and 27 in Fig. 3. As illustrated in Figs. 1 and 2,the extending lugs in each of the rows 15 and 16 are staggeredvertically in order to permit three independent groups of resistors tobe supported and arranged as indicated in the drawings.

By having several independent groups of resistors 23 supported as shownin Fig. 2, it is possible to have the same heat distribution in thebottom of the furnace as in the top, by reason of the symmetricalarrangement of the extending lugs located in rows 24, 25, 26 and 27.When the furnace has attained the required temperature, partof theresistor groups may be taken out of the circuit entirely and one or twogroups only, as may be required to compensate for the radiation lossesof the furnace, may be left in the circuit in order to maintain apredetermined constant temperature. It is also possible by means of thisarrangement to have a constant power circuit which is energized at alltimes during normal operation of the furnace and is designed to takecare of substantially the radiation losses only, whereas the otherresistor groups may be in a temperature-controlled circuit whereby thedifference between the on and olf temperatures may be decreased todesirable limits without materially affecting the heat distribution ofthe resistors.

rIhe device embodying my invention provides a relatively simple meansfor uniformly spacing independent groups of resistors of equal lengthswithin the furnace chamber of electric furnaces. |The supports may bedesigned with two, three or four, or a plurality of rows of inwardlyprojecting lugs which are integral with an outwardly extending portionthat is adapted lo lit into the walls of the furnace proper. Each of theinwardly projecting lugs are staggered vertically with respect to thehorizontal parallel rows formed by the above inwardly projecting lugswhereby the individual groups of resistors will have alternately similarrecurring groups of return-bent loop portions formed by' the resistorsas they are bent to fit or to conform with the arrangement of thesupports. This arrangement permits of connecting the groups in series,parallel or series-parallel arrangement and ensures equalized heatdistribution irrespective of the connections employed.

`Various other modifications of my invention may be made withoutdeparting from the spirit and the scope thereof. I, therefore, desirethat only such limitations shall be placed thereon as shall be imposedby the prior art.

I claim as my invention:

1. In an electric furnace, the combination with a furnace chamber, of aplurality of refractory wall members and a plurality of resistorssupported by said refractory wall members in such manner that thedepending loop portions along each of the walls are alternately similar.

2. In an electric furnace, the combination with a wall, a plurality ofindependent members extending laterally from said wall in rows one abovethe other, and resistors so disposed in groups along each of the wallson said laterally extending members that they are equally spaced inalternately recurring symmetrical arrangement.

3. In an electric furnace, the combination with a furnace chamberenclosed by a plurality of refractory walls, a plurality of independentresistor groups having similar alternately recurring depending loopportions, and a plurality of refractory supporting members secured tosaid walls, a plurality of refractory spacing members, extendinglaterally into the furnace chamber from said refractory walls in rowsone above the other, whereby the resistor groups are so supported andequally spaced that the top and bottom return-bent loop portions occuralternately in similar group relation.

4. In an electric furnace, the combination with a plurality ofrefractory walls enclosing a furnace chamber, a plurality of refractorysupporting members extending therefrom in rows one above the otheradjacent to the upper part of said walls, a plurality of refractoryspacing members extending laterally from the walls in rows one above theother adjacent to the lower part of the walls, and a plurality ofindependent resistors, having top and bottom return-bent loop portions,supported from the refractory members adjacent to the top of said wallsand uniformly spaced apart by said refractory members adjacent thebottom of said walls, whereby the top and the bottom loop portions occuralternately in similar grouped relation. A

5. In an electric furnace, the combination with a plurality ofrefractory walls enclosing a furnace chamber, a plurality of refractorymembers extending laterally therefrom in two pairs of parallel rowsspaced one above the other, one pair of parallel rows being locatedadjacent to the top and the other pairof rows located adjacent to thebottom of said walls, and a pair of independent resistors, having aplurality of depending loops portions supported from the said refractorymembers of the upper pair of rows by the upper return-bent loops andspaced apart by the refractory members of the lower pair of rows.

6. In an electric furnace, in combination with a plurality of refractorywalls inolosing a furnace chamber, aplurality of refractory membersstaggered vertically and extending laterally into the furnace chambertherefrom in a plurality of parallel rows adjacent to the top and thebottom of said walls, and a plurality of independent resistors, havingreturn-bent top and bottom loop portions with substantially straightparts therebetween, supported from the loopkof the top return-bent loopportions and spaced uniformly apart at the lower loop portions, wherebythe said top and bottom returnben-t loop portions occur alternately insimilar grouped relation. p

In testimony whereof, I have hereunto Subscribed my name this 17th dayof September, 1925.

JAMES C. WOODSON.

